Sorex ornatus sinuosus, the Suisun shrew or Suisun ornate shrew, is a subspecies of the ornate shrew that occurs in the tidal marshes of the northern shores of San Pablo and Suisun bays (northern arms of the San Francisco Bay, as far east as Grizzly Island and as far west as the mouth of Sonoma Creek in the vicinity of Tubbs Island). Brown and Rudd redefined the western boundary of the range from a prior designation of the Petaluma River. The Suisun shrew has been designated as a Species of Concern by the U.S. government and a Mammalian Species of Special Concern by the state of California.